Information drives business. Companies today rely to an unprecedented extent on online, frequently accessed, constantly changing data to run their businesses. Unplanned events that inhibit the availability of this data can seriously damage business operations. Additionally, any permanent data loss, from natural disaster or any other source, will likely have serious negative consequences for the continued viability of a business. Therefore, when disaster strikes, companies must be prepared to eliminate or minimize data loss, and recover quickly with useable data.
Companies have come to rely upon high-availability clusters to provide the most critical services and to store their most critical data. In general, there are different types of clusters, such as, for example, compute clusters, storage clusters, scalable clusters, and the like. High-availability clusters (also known as HA Clusters or Failover Clusters) are computer clusters that are implemented primarily for the purpose of providing high availability of services which the cluster provides. They operate by having redundant computers or nodes which are then used to provide service when system components fail. Normally, if a server with a particular application crashes, the application will be unavailable until someone fixes the crashed server. HA clustering remedies this situation by detecting hardware/software faults, and immediately restarting the application on another system without requiring administrative intervention, a process known as Failover. As part of this process, clustering software may configure the node before starting the application on it. For example, appropriate file systems may need to be imported and mounted, network hardware may have to be configured, and some supporting applications may need to be running as well.
HA clustering and failover clustering are commonly used to implement highly scalable cloud environments. In a cloud environment, multiple virtual machines may be cloned, provisioned and replicated to a remote cloud along with the application data. Virtual machines cloned from the parent will have substantial common data between the two and multiple such virtual machines that belong to different replication volume groups (RVG) may be replicated to the same remote site. Replicating common blocks will increase the initial synchronization time and utilize additional network bandwidth.